How i can used from "Invalidate(System.Drawing.Region region)"?

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C#

hi. i write a paint software. i want redraw shape when i draw new shape.
i used from "invalidate()" and then draw all shape again. for improve the paint, i want that just the region that the new shape is drawing, be redrawing. i want used " Invalidate(System.Drawing.Region region)" for this purpose but i dont know how i define and used region. please help me. do this way do my purpose?!
this work is for a user control that i want paint on this.